Ask someone what experiments at the CERN-LHC do, they will tell you: ‘You accelerate two protons to very high energy, smash them together and look in great detail at all particles created from the disintegration of the protons.’ etcetera. Well… yes… mostly.
The CMS collaboration has substantially improved the precision with which the top quark mass is measured. The latest result, a measurement of the top quark mass of 171.77 ± 0.38 GeV, was presented at CERN last week and estimates the value of the top quark mass with a precision of about 0.22%. The gain comes from new analysis methods and improved procedures to consistently treat uncertainties in the measurement simultaneously.
In heavy ion collisions, for ultra-peripheral processes, simultaneous emission of photons by oppositely moving 2 lead ions can occasionally produce a pair of tau leptons. The CMS Collaboration has observed such a phenomena, for the first time in the LHC data. The results were presented in the recently concluded Moriond and Quark Matter conferences.
Running toward the start of Run3 at the Large Hadron Collider (LHC), the CMS experiment completed one of its last and crucial steps: the big solenoid magnet has been powered on to reach the nominal magnetic field of 3.8T on March 4th 2022.
State-of-the art machine learning techniques have been used by scientists of the CMS collaboration to identify efficiently the hadronic decays of the tau leptons vis-a-vis jets (sprays of particles boosted in a given direction). This will help the CMS experiment in a big way to discriminate quickly, in real time of the LHC collision, the physics processes involving tau leptons and extract interesting physics from the collected data subsequently.
Physicists at the CMS experiment have been searching for new particles in exciting new places. In a recently published paper, they explore the possibility that the Large Hadron Collider (LHC) could be producing never-before-seen particles that travel into the CMS detector before transforming into known particles. And because no one knows for sure what undiscovered particles might look like, the scientists design the search to be as simple as possible to make sure it can test many theories at once, including ones that have yet to be imagined.
CMS experiment recently made a new measurement of Higgs boson coupling strength to the charm quark, putting the best constraint so far on the anomalous value compared to the prediction from the standard model. Using the complete data volume of Run 2, and using state-of-the-art techniques of machine learning aptly, the scientist developed a very sensitive methodology for identification of jet originating from a charm quark. Further by taking into account all possible values for the Higgs boson momentum being low or high, they considered distinct possibilities for the two jets from the Higgs boson decay being separated or collapsed in space. Again deep learning methods helped here to achieve the goal.
A few months are left before the start of Run 3 at CERN. With the timely completion of all upgrades planned for Long Shutdown 2 (LS2), in the last weeks the CMS detector has been set in its closed configuration.
The challenge of Run3: CMS is preparing to resume its operations for the Run-3 of the Large Hadron Collider (LHC) after a 3-year long shutdown called LS2 (2019-2021).
